The present invention is directed to a method for embossing materials. More particularly, the present invention pertains to a method for converting deep or textured patterns having a thickness of greater than 200 nanometers into shallow relief embossing shims for use with conventional holographic film embossing equipment.
Embossing is used to physically imprint images such as 3D microstructures or holographic images, onto material or film. Traditional embossing applies pressure to the backside of a material to alter the surface, giving the material a three dimensional or raised effect. In other words, traditional embossing transfers the 3D microstructure or hologram to the material. Typical film embossing machines use two cylindrical rollers, an embossing roller and a backing roller. An embossing stamper with a textured pattern, also known as an embossing shim, is attached to the embossing roller. Film, generally between 0.0006 and 0.001 inches thick or with greater, is pushed or pulled between the two rollers. The raised or textured embossing shim located on the embossing roller forces the film against the backing roller to create the embossed impression on the film. The embossed side of the impression may then be aluminized or metalized to turn the 3D microstructure into a reflection hologram. The film, with or without the metalization, can later be laminated to paper, cardboard, plastic, metals, or other substrates.
A textured pattern, also known as a relief, having a deep or thick profile greater than 400 nm usually cannot be embossed directly onto a substrate using traditional holographic embossing techniques, such as embossing rollers, because the quality of the product diminishes with increasing thickness of the 3D microstructure. Instead, if a deep relief, such as the grains of wood or brushed metal, for example, is desired, a brushed metal or other simulated relief is produced by physically brushing the film to simulate the texture or UV cast embossing to replicate the image onto the film. While effective, UV casting to accommodate texture patterns with a thickness or depth greater than 400 nm, or creating physical/actual texture can be cumbersome.
In some circumstances however, it is not necessary to have the actual total depth of the image embossed in the film. An image or impression which simulates the look of depth, without having the actual depth, can be sufficient to convey the design or texture desired.
Accordingly, there is a need for a way to simulate the look of deep or textured materials that have a thickness of greater than 400 nm on a material or film using conventional high speed embossing equipment. Such a method would utilize embossing shims having images which simulate the look of the thick or deep, three-dimensional reliefs. Desirably, such a method enables the embossing shim to be used on conventional high speed film embossing equipment. Furthermore, it is desirable that the embossing shim is easy to make and gives the same or similar effect of a three-dimensional image without having the bulk of a deep texture or pattern inhibit the use of conventional equipment.